A low-repetitive 2.2 kb sequence has been isolated from the human genome. Based on preliminary studies, we suspect that this sequence is a mobile or transposable element. The major aim of this proposal is to confirm this hypothnesis and to discover whether or not this sequence is a part of or regulates the expression of other genes. Toward this end, we propose: 1) to sequence a cloned 2.2 kb repetitive DNA element and related members of its family. M13 cloning and Sanger's dideoxy" sequencing procedure will be used to obtain nucleotide data which will be analyzed for open-reading frames, conserved sequence, and other features which resemble retroviruses and transposable elements. 2) to study the organization of this repeat family as it appears in various portions of the human genome. Lambda libraries of human chromosome 12 will be screened for recombinants which hybridize to the 2.2 kb sequence. DNA from such recombinants will be compared to the 2.2 kb sequence in terms of organization and degree of cross-hybridization. 3) to study transcripts of the repeat family by Northern blot analysis of RNA from various cells and tissues and by screening preexisting cDNA libraries. Northern blot analysis of RNA from different sources will give us information on the sizes and types of transcripts. Analysis of cDNA clones containing sequences homologous to the 2.2 kb fragment will reveal whether the repetitive element alone is transcribed or only in conjunction with other genes. 4) to explore the use of the 2.2 kb repetitive sequence family as markers for genetic studies. Family members will be used for regional mapping of human chromosomes 12 and 21 and further extended to the detection of small deletions and restriction fragment length polymorphisms. These studies will result in information regarding the relationship of a class of repetitive sequences to regulation, differentiation and development in the human genome. Also, these cloned repetitive elements mayt have application to medicine in their use as genetic markers for the detection of genetic and developmental diseases, including cancer.